1. Field of the Invention
The present invention relates generally to a self contained lamp control and lamp package, and relates more specifically to a self contained lamp for automatic light level adjustment.
2. Description of Related Art
Referring to FIG. 1, a conventional incandescent light bulb 5 includes base 10, and evacuated envelope or diffuser 14. Diffuser 14, which is typically pear-shaped, surrounds a filament (not shown) that is electrically connected to base 10 for electrical connection to a conventional lamp socket. A well-known base is an Edison screw-base, as shown, which is electrically connectable to an Edison screw socket.
In recent years, compact fluorescent lamp packages have been introduced into the market. These lamp packages are particularly desirable because of their energy efficiency.
Referring to FIG. 2A, an example prior art compact fluorescent lamp package (CFLP) 7 is shown consisting of fluorescent lamp 12, lamp holder 13, and auxiliary housing 15 for interfacing between lamp holder 13 and base 10. Typically, housing 15 also houses a complete ballast 17. However, it should be noted that ballast 17 has also been placed into base 10, while either retaining housing 15 or removing this housing. In most CFLPs an Edison screw-base is used as base 10 for a reliable mechanical and electrical connection to a standard Edison socket, although other sockets are known and used.
The typical height of a standard incandescent light bulb 5 is about 4.5 in. However, most conventional CFLPs are typically taller than a conventional incandescent light bulb due to auxiliary elements such as auxiliary housing 15. As a result, a conventional CFLP may extend out of a lampshade or fixture adapted for an incandescent light bulb, causing an undesirable appearance, or the CFLP may not fit within an existing fixture. This extended height, together with the unusual appearance of conventional CFLPs, are believed to adversely affect the acceptance of CFLPs in the marketplace.
Another issue with the conventional CFLP is that when ballast 17 is housed in auxiliary housing 15, the heat generated by ballast 17 cannot escape very efficiently. Referring, for example, to FIG. 2B, in a typical enclosure or downlight fixture 19, the heat generated from the lamp and ballast of a conventional CFLP 7 collects up in the fixture around the CFLP 7 without any path to escape.
As a result, there is a higher ambient temperature around CFLP 7 which causes the internal components of the CFLP 7, especially ballast 17, to run at even higher temperatures, e.g., above 150° C. The increase in the internal heat decreases reliability, causes field failures and limits the use of a conventional CFLP to open rather than enclosed fixtures, all of which further adversely affects the desirability of CFLPs. Nonetheless, it should be noted that when ballast 17 has been placed into base 10 as described above, the base has acted as a heat sink for the ballast, helping to dissipate some of this heat.
A further issue with the conventional CFLP is that because of its size and operational constraints, such as its high ambient temperature and its use of the conventional Edison socket, it is difficult to realize some desirable features, such as, for example, a dimming feature where the light output of the fluorescent lamp is selected based on a control signal or setting. More specifically, conventional incandescent lights typically use a dimmer control mounted on a wall near an on/off switch for adjusting the light level. These types of dimming controls operate on various principles but all in essence change the characteristic of the electrical power supplied to the light fixture to create various power levels supplied to the lamp, thereby affecting the output lighting level. However, these types of dimming controls are unsuitable for CFLPs because the change in power may extinguish the lamp. As a result, in order to incorporate a dimming feature into the CFLP, a dimmable ballast circuit is typically used where the electronic ballast now includes an additional dimming function that controls the ballast to dim the lamp. However, a mechanism is now needed to control this additional dimming function, thereby making it a difficult challenge to provide a dimming feature to a CFLP.
For example, one mechanism that has been used to control a dimmable ballast circuit is to dedicate a wire from a wall-mounted dimmer to the fixture. However, if the CFLP is inserted into an Edison socket, this requires additional wiring. Specifically, Edison screw sockets typically only provide switched utility power on two wires, a line input and a neutral wire. Accordingly, a third wire is now needed to control the dimming function. However, providing a third wire or connection to the Edison screw socket is a highly undesirable additional requirement to realize a dimming feature.
Another example mechanism that has been used to control a dimmable ballast circuit is to send control signals from a switch to the fixture directly over the power lines, thereby negating the need for an additional wire. However, this approach is complex, expensive, and space consuming given that the fixture must now include an interface to receive and decode the signal. Nonetheless, it should be noted that some systems that have used this mechanism have also incorporated advantageous features, including the use of an external control module that allows for the remote and automatic control of the lights. For example, a control system may be provided that can control a number of different areas of lighting to automatically change lighting settings depending upon various circumstances, such as evening hours, weekend hours, lengthened days and so forth. However, it should also be noted that these types of lighting systems typically have limited local intelligence (e.g., the fixtures lack sensor feedback that permits localized control) and often control blocks of lights together, rather than individual lights.
Another mechanism that has been used to control a dimmable ballast circuit is to include a manual control directly on the casing of the electronic ballast of the CFLP so that dimming can be effected. However, CFLPs designed to replace incandescent bulbs often do not permit easy access to the CFLP or electronic ballast by the user. In addition, once the light level has been set, it is often difficult or inconvenient to readjust.
A further mechanism that prior fluorescent light systems in general have used to control dimming is to incorporate a self-dimming function that automatically dims the light in reaction to external events. Such self-dimming functions have included the integration of a heat sensor or a photosensitive control element, such as a photocell, with the dimming function. For example, these systems have interconnected a photocell with the dimming function to automatically control the turning on/off of the light and to maintain a constant light level in a room, all based on the changing ambient light levels in the room.
In the case of the CFLP in particular, the photocell has been mounted directly on the housing 15. This arrangement creates several advantages as compared to the other dimming mechanisms described above. Specifically, this arrangement allows for individual control of each CFLP and because of the automatic feedback orientation, each CFLP is self-dimming thereby making the CFLP easier and more convenient to use because the user is not required to constantly readjust the light level as conditions change. In addition, when the CFLP is inserted into an Edison socket, the socket does not require additional wiring. This mechanism is also less complex and less expensive than prior mechanisms.
Nonetheless, prior CFLPs that have integrated a sensor, like a photocell, with the dimming function of a dimmable ballast circuit continue to have the same issues as described above with reference to the example CFLP 7. Specifically, these prior CFLPs continue to use a housing 15 to house the dimmable ballast circuit, thereby creating the same height and heat issues described above.